A spot by MoveOn.org aims to tar Republican candidates for having the backing of the U.S. Chamber of Commerce — part of a broader Democratic broadside against the organization for the funding it gets from outside the U.S.

"Where has the chamber been getting some of their money lately? From foreign corporations in countries like China, Russia and India," warns the narrator as ominous music plays over a map of the Eastern nations. "Exactly who is Mark Kirk working for? Because it sure isn't Illinois."

In Louisiana, an ad for Sen. David Vitter a Republican, features what appear to be Mexican immigrants sneaking through a hole in a chain-link fence — only to be greeted by a group of people with balloons and a banner reading "Charlie Melancon welcomes you to the USA," a reference to his Democratic opponent.

The anti-foreign appeals come as candidates try to play off voter fears about ebbing U.S. influence, a potent concern at a time of high unemployment.

"This is certainly the proper petri dish for this stuff to grow in," said David Doak, a veteran Democratic media strategist. "Anytime you've got difficult economic times, you've got people who are frustrated and angry about their own situations, and the natural human instinct is to look for someone to blame."

The negative tenor has been amplified by this year's swelling number of political ads. Total spending on television commercials in local, state and federal races is expected to reach a record $3 billion, up from $2.7 billion in 2008 and $2.4 billion in 2006, according to Campaign Media Analysis Group, a division of Kantar Media that tracks political advertising.

Richard Haass, president of the Council on Foreign Relations, said the election-year rhetoric would further bog down efforts to pass immigration reform and approve trade agreements with Colombia, Panama and South Korea.

"In most instances, what is claimed is simply wrong and it's actually getting in the way of our adopting policies that would help us economically," said Haass, noting that similar anti-foreign sentiment is on the rise in many European countries. "It's not unique to the United States. It's simply a phenomenon of what happens in open societies when there is fear and unhappiness."

Scapegoating outsiders is a long-standing tradition in American politics, stretching back to Colonial days. More recently, "we saw this in the '80s with Japanese car manufacturers and in the '90s with jobs going to Mexico," said Evan Tracey, president of Campaign Media Analysis Group.

This year, China is a prime target. A commercial by the Democratic Senatorial Campaign Committee accuses Republican Pennsylvania Senate nominee Pat Toomey of "working to bring jobs — to China," a notion punctuated by the sound of a gong. The ad ends with a fortune cookie breaking and revealing the message "Pat Toomey. He's not for you."

In North Carolina, a spot by GOP House nominee Harold Johnson accuses Democratic Rep. Larry Kissell of voting "to give tax credits to firms employing foreign workers in communist China." The National Republican Congressional Committee has taken a similar tack in a spate of ads against House Democrats, seizing on a study last spring that found a majority of grants for wind farms in the stimulus bill went to foreign companies.

Meanwhile, Democrats are seeking to tie their rivals to foreign corporations, suggesting that companies from abroad could be funneling money to third-party groups spending big in this year's election. "It's incredible: Republicans benefiting from secret foreign money," an ad by the Democratic National Committee says as Chinese yuan bills pile up on the screen.

That allegation has drawn vehement objections from Republicans, who have argued that there is no evidence of such foreign influence. But Democratic leaders show no sign of backing off: A survey last week by Democratic pollster Stanley Greenberg found that when combined with a message about Republican support for free trade, the attack was particularly effective with seniors, non-college-educated voters and urban dwellers.

Muslims have also emerged as political bogeymen, as some Republicans have sought to exploit the controversy over the building of an Islamic community center near the site of the former World Trade Center in New York.

"After the Muslims conquered Jerusalem and Cordoba and Constantinople, they built victory mosques, and now they want to build a mosque by ground zero," intoned a spot for Renee Ellmers, a North Carolina Republican running for the House. The ad accused Democratic Rep. Bob Etheridge of not taking a stand on the mosque. (His spokesman said Etheridge did not think it was a good idea to build the center close to the site of the World Trade Center attack.)

Political analysts warned that voters should brace for the nastiness to get worse.

"There have been your hard-hitting charges, but in terms of downright offensive, just wait," said Jennifer Duffy, who monitors the Senate for the Cook Political Report, a nonpartisan newsletter in Washington. "The really over-the-top, crazy, offensive stuff, we're going to see in the next two weeks."